This invention relates generally to apparatus for preventing or overcoming binding which can occur between a sewing machine needle and material that is being sewn thereby. The invention relates more particularly, but not by way of limitation, to devices which prevent or limit the upward movement of a presser bar of a sewing machine when the material being sewn becomes bound with the sewing machine needle.
When a sewing machine is used to sew such a material as leather, the sewing machine needle can bind with the material and pull it upward away from the workpiece support table of the sewing machine as the needle is retracted from its stitch-producing position. The adherence of the material to the needle is often sufficiently strong to overcome the downward force exerted by a presser bar and an accompanying presser foot which form part of the sewing machine.
This binding and upward movement of the material is troublesome to the sewing machine operator because the sewing operation must be interrupted to manually separate the material from the needle so that proper sewing can proceed. Additionally, when the material overcomes the force exerted by the presser bar and foot, the two pieces of material to be sewn together become misaligned. This misalignment likewise slows the operation because the operator must take additional time to realign the two pieces of material.
Therefore, there is a need for an apparatus which can be attached to or incorporated with a sewing machine for preventing or overcoming the binding force which can arise between a sewing machine needle and the material to be sewn. More specifically, there is the need for an apparatus for limiting the displacement of a presser bar and its accompanying presser foot so that they will not be excessively moved should binding occur. Such an apparatus is particularly needed on domestic sewing machines which are not originally constructed to overcome binding which may occur between the needle and the material to be sewn.
Although I have proposed other types of sewing machine conversion apparatus for converting a domestic machine into one capable of sewing relatively heavier materials (see my copending U.S. patent application Ser. No. 081,345 filed Oct. 3, 1979, my U.S. patent application Ser. No. 159,109 filed June 13, 1980, and my U.S. Pat. No. 3,952,675 issued Apr. 22, 1976), none of these meets the aforementioned needs. I am aware of no other proposed or constructed devices which meet these needs.